Urethane adhesives are used for bonding automotive fiberglass reinforced parts. Recent adhesives have been developed which have high bonding strength without the need for surface treatment of the fiberglass reinforced part as in U.S. Pat. No. 4,876,308. Such an adhesive in high temperature applications, e.g., paint bakes at temperatures of 400.degree. F. (204.degree. C.), degrades and results in fiberglass reinforced plastic assemblies having undesirable bond strength.
U.S. Pat. No. 4,876,308 to Melby et al. relates to a two-component type polyurethane adhesive for fiberglass reinforced plastics which requires no cleaning, preparation or treatment of the surface, and the like. The curative component is a nitrogen-free liquid polyether or polyester in an amount such that in association with a urethane prepolymer component containing free NCO groups, the ratio of the free NCO groups in the prepolymer component to the OH groups and NH groups in said curative component is at least 1.2 and desirably at least 1.35.
Thermal oxidative stability of polyurethane compositions at a high temperatures has been studied.